Does living on Earth not also for human beings mean being open to the sky? Watching day alternate with night, relying on the seasonal cycle, finding their way according to the position of the stars, humans have always been aware of their dependence on the sky and tried to understand the origin of life in relation to it. And it is up to the sky again that their imagination and thoughts fly whenever they feel cramped in their earthly habitat. Following the axis of their own vertical position, the earth that is the floor for humans is seen as a ‘down here’ by opposition to an ‘up there’, the sky, towards which they turn their heads and raise their eyes. Up there is the origin of the metaphorical figure and /or dream image of the flight up into the high heavens, or the journey to other stars, or to a spiritual land beyond.

In his study of the conversion of Westerners to Islam, a Turkish sociologist revealed in 1996 that it happened that a significant proportion of the converts had adopted that religion under the influence of Islamic mysticism, or Sufism. Now Sufism, located at the meeting-point of the written and oral traditions of Islam, offers an original commentary on the Quran and a spiritual practice based on psychosomatic exercises close to yoga. Interest in Sufism among Westerners was revealed at the end of the nineteenth century and became considerable from the 1930s onwards, resulting in the foundation in Europe of Sufi groups directed by converts who very quickly became shaykhs (shaikh). These first groups, to which new ones were added, are still active today, although somewhat bruised by numerous divisions. The reasons for conversion to Sufism among Europeans, for the most part from intellectual milieux, rest on concerns of a spiritual dimension linked to the climate of religious crisis which the modern West has experienced since the end of the nineteenth century. To which should be added in recent decades the fashionable exoticism fostered by the development of means of transport and communication which have brought East and West closer.

Until the beginning of the twentieth century Christianity, in order to proclaim its message, was based above all upon the word, the substance of prayer and preaching; certainly manuscripts, with the Scriptures and other fundamental texts, long secured the foundations of the faith, but before the advent of printing their diffusion and reception remained the prerogative of lettered elites, most often clerics such as the Benedictines (remember Umberto Eco's famous novel published in 1980, The Name of the Rose). Moreover, the Catholic Church made extensive use of the image in the Middle Ages, above all in the gothic period, and created remarkable visual splendour in its holy places. Stained glass windows and paintings and sculptures with subjects from the Old and New Testaments reinforced the devotion and faith of the illiterate. It was only after 1450, with Gutenberg's invention of printing - which, moreover, immediately disseminated bibles, missals and prayer-books - that the text became a major means of transmitting the Christian message. From the sixteenth century onwards Protestant Calvinists (but not Lutherans or Anglicans) rejected religious imagery - even the crucifix - as a means of devotion, for they were considered idolatrous; on the other hand, the reformers, more than the Catholic Church, laid stress on the reading of biblical texts by the faithful, especially the Old Testament, henceforth much more widely distributed, thanks expressly to printing. Admittedly the word did not lose its rights; like Catholicism in its churches and cathedrals, the Reformation preached the Good Word in its temples. Yet paradoxically, the present return of the religious image - this time televisual - was to be first of all a Protestant occurrence, principally in the United States.

The source of my interest in the study of heresiology originates in many years of research on the work and life of Meister Eckhart. It is therefore in an Eckhartian perspective, which presupposes a certain leniency, and even sympathy, towards the phenomenon of heresy, that I am going to give a survey of ‘the other side of Christianity’, from the Acts of Simon Magus, ‘father of heresy’, to the dawn of the second millennium, while exposing the medieval period in greater depth.